Caesar’s Legion is an imperialist organization, led by the charismatic, cunning, and powerful Caesar. The legionaries are a well-organized, jingoistic fighting force that mainly operate east of the Grand Canyon and in Arizona. The Legion is composed mostly of reconditioned tribals and their young offspring.

Edward Sallow, who would be known as Caesar, was born in 2226. His family once lived near the Boneyard until his father was killed by raiders when he was two years old, forcing his mother and him to flee - eventually finding sanctuary with the Followers of the Apocalypse in 2231. He received a free education from the Followers and eventually became a full member - a scribe specializing in anthropology and linguistics (though he is also well-versed in modern history, as evidenced by his knowledge of the Enclave).

In 2246, at the age of 20, Sallow and Bill Calhoun, a fellow Follower, were sent east to study tribal dialects (which he considers, in hindsight, a waste of time). He was instructed to meet with a Mormon missionary named Joshua Graham who was a tribal specialist. They then embarked on a journey to the region known formerly as Arizona as part of a nine-person expedition. During this expedition, they also discovered a cache of books about Ancient Rome. While he had known some basic facts about ancient history, these books shed new light on some of the details. Reading first The History of the Decline and Fall of the Roman Empire and then Julius Caesar's own Commentarii, personal accounts of his military conquests, changed his life and was the starting point of his grand plan. He intended to use the Commentarii as a blueprint - after all, which illiterate tribal would know that he was not the original Caesar, and his "Rome" was merely a copy of a civilization long gone.

At some point in 2247, Graham, Calhoun and the future Caesar were staying with the Blackfoot tribe. For an unconfirmed reason, the expedition was not allowed to leave. At the time the tribe was at war with seven other tribes, a war they were inevitably going to lose. Unwilling to be destroyed along with them, and against the wishes of his companions, Caesar chose to use his knowledge to train the Blackfoot tribe in the art of warfare after witnessing their lack of knowledge first hand. He showed them how to clean and maintain guns, operate with small unit tactics, create their own explosives and to strike at their weakest enemies first: divide et impera - divide and conquer. He quickly impressed them enough to the point where he was made their leader and took the name "Caesar". Free to go, Joshua Graham preferred to stay with Caesar and was recruited by him as a translator first, rapidly becoming their leader in battle.

He soon introduced the concept of total war to the tribes around them - Caesar knew that though the tribes had always fought each other via occasional skirmishes, he considered them to only be "playing at war" and did not face warfare at its most destructive and barbaric extent. The concept of total war was an entirely new and terrifying facet to his strategy that they had never confronted before and would form the core of the Legion's tactics and outlook. They defeated the weakest of their enemies first, the Ridgers, and enslaved many of the able-bodied survivors but Caesar had the rest, including women and children, killed and their remains piled high. When they confronted the next tribe, the Kaibabs, they brought an emissary back to view the carnage. Eventually, all seven tribes were either destroyed or incorporated in what now became known as Caesar's Legion, founded by Caesar himself and Graham.

A member of the Legion

Joshua Graham became Caesar's right-hand man and the first Legate, now known as the Malpais Legate. While Calhoun was sent back to the Followers to inform them of what he was doing, the other six members of the expedition were killed on the self-proclaimed Emperor's orders. Caesar formed his Legion out of the tribes that had either been conquered or had chosen to capitulate to avoid total destruction. He chose the concept of the Roman Empire to model the Legion after because of its parallels to what he considered the status-quo of the post-apocalyptic world. Ideologically, the Roman Empire was also appealing to him for its ability to assimilate those it conquered, the destruction of such "tribal" identities a key goal to the Legion's long-term strategy of unification. He intended to erase their individual identities and replace them all with a single, monolithic culture - the Legion - where individuals have no value outside of what they offer the greater whole - long term stability at all costs.

By 2250, Caesar had declared himself the son of Mars, Roman god of war, and five years later he established his first capital in the ruins of Flagstaff, Arizona. Together with the Malpais Legate, he used the power base they established to attack and assimilate more tribes into the Legion. For decades, they fought and absorbed inferior tribes, erasing tribal identities and shaping them into a massive, fanatically loyal army that, in Caesar's eyes, embodies the concept of a perfect post-nuclear society. By 2274, he had conquered most of the tribes of northern Arizona, southwestern Colorado, western New Mexico and southwestern Utah, and became known as the "Conqueror of the 86 Tribes" whose Legion had never met any serious defeat until their confrontation with the New California Republic.

The NCR would have the dubious distinction of being recognized by Caesar as a worthy adversary. Though the Legion would attack and torture Corporal Sterling, his first attack on the NCR, the NCR would be ignorant of his presence. Despite further attacks, the NCR would continue to ignore Caesar. When the NCR was in the heart of the NCR-Brotherhood War, they would realize Caesar and his troops amassing alongside the Colorado River and would finally perceive Caesar as a threat. Caesar views his campaign against NCR as similar to that of his namesake Julius Caesar who eventually seized power for himself after crossing the river Rubicon and capturing Rome and fighting the Roman Civil War.

The Legion would declare war on the NCR by succeeding in destroying one of their major fortifications, Fort Aradesh, Legion forces under the command of the Malpais Legate marched against the NCR garrison at Hoover Dam, in an attempt to take the strategic asset and river crossing. In what became known as the First Battle of Hoover Dam, Legate Graham initially had the upper hand. Graham was able to push the NCR defenders back and lead his forces over the dam. Lead elements of the NCR, including members of the 1st Recon Battalion and NCR Rangers, executed a tactical retreat west across the dam and into Boulder City, all the while using their prowess in marksmanship to kill the Legion officers (primarily Centurions and Decani). Graham, unable to adapt strategies in combat, chose to order his legionaries to push the rangers, not knowing the NCR had booby-trapped Boulder City, laying explosives along their line of retreat, and drawing the Legion into a trap. When the Legion forces entered the city, the NCR detonated the explosives and inflicted severe casualties among the Legion forces, crippling their offensive. The NCR forces then counter-attacked, pushing back and eventually routing the Legion forces who fled east back over the dam. Caesar, angered at the failure of his Legate, made an example of him. The Praetorian Guard, Caesar's elite bodyguards, covered Legate Graham in pitch, set him on fire, and cast him into the depths of the Grand Canyon.

By 2281, Caesar's Legion has reestablished its power in the west and is slowly encroaching on the city of New Vegas. They continue to contest NCR over all of the region, destroying several NCR bases such as Ranger station Charlie and Camp Searchlight, and creating unease and terror in the remaining bases. But the Caesar's Legion desires two things now: an equivalent of Carthage and an equivalent of Rome. In the NCR he has at last found a grand adversary, against which he can wage a military campaign worthy of history books; in Vegas, he has at last found a capital which he feels is truly worthy of being the keystone of a new great empire. His end goal is to return to his place of birth in the NCR and establish a new order with himself as total ruler. Caesar hopes to one day destroy the NCR senate and replace it with his dictatorship, just as Augustus Caesar himself had done to the Roman Republic over two thousand years prior.